1. Field of the Invention
This invention relates to an improved process for the preparation of an N-substituted unsaturated carboxylic acid amide (hereinafter called "N-substituted amide") represented by the following formula (A): ##STR2## wherein R.sup.1 means a hydrogen atom or methyl group, Y denotes a methylene group, oxygen atom or methylimino group, m and n stand individually for an integer of 0 to 5, and m+n is an integer of 3 to 5.
2. Description of the Related Art
The above-described N-substituted amides are useful compounds having a wide variety of utility, such as, water-absorbing agents, non-fogging agents, condensation preventives, isolation membranes, resin modifiers, etc.
An N-substituted amide can generally be prepared by aminolysis of an unsaturated carboxylic acid ester with an amino compound. Michael addition, however, takes place to the double bond of the amino compound upon aminolysis of the unsaturated carboxylic acid ester with amino compound, so that the selectivity to the intended product is low. Reformation of a double bond from the Michael addition product requires a step such that pyrolysis is effected at a temperature as high as 180.degree. to 300.degree. C. so as to release the amino compound thus added. Side reactions such as formation of polymers take place in the step, whereby the yield of the intended product is lowered significantly (Japanese Laid-Open Patent Application No. 111016/1975).
In order to suppress these side reactions, it has been proposed to obtain an intended product by first of all adding a lower alcohol to each double bond, conducting aminolysis and then effecting de-alcoholization at an elevated temperature to re-form the double bond again (Japanese Laid-Open Patent Application No. 66623/1974; U.S. Pat. Nos. 2,534,585; 2,702,822). Although the above method is effective for the objective of preventing Michael addition of the amino compound to the double bond, it is accompanied by a drawback that side reactions, such as, polymerization, take place upon re-formation of the double bond by the de-alcoholization reaction and the yield of the intended product is hence reduced.
As a method for protecting a double bond, it has been known to add cyclopentadiene to the double bond by a Diels-Alder reaction. After completion of aminolysis, the cyclopentadiene is removed by pyrolysis (Japanese Laid-Open Patent Application No. 66625/1974, etc.). Formation of byproducts still cannot be avoided even by this method. Further, this method requires steps for the separation and recovery of the removed cyclopentadiene from the intended product. Moreover, it is impossible to completely avoid admixture of a trace amount of cyclopentadiene into the final product.